Packaged semiconductor dies, including memory chips, microprocessor chips, and imager chips, typically include a semiconductor die mounted to a substrate and encased in a plastic protective covering. The die includes functional features, such as memory cells, processor circuits, imager devices, and interconnecting circuitry. The die also typically includes bond pads electrically coupled to the functional features. The bond pads are electrically connected to pins or other types of terminals that extend outside the protective covering for connecting to busses, circuits, and/or other microelectronic assemblies.
Market pressures continually drive manufacturers to reduce the size of semiconductor die packages and to increase the functional capacity of such packages. One approach for achieving these results is to stack multiple semiconductor dies in a single package. In such packages, the stacked dies can be electrically coupled together using conductive vias that extend through the entire thickness of the dies. The conductive vias are generally referred to as through silicon vias or TSV.
Conventional processes for forming TSVs include patterning a semiconductor substrate, etching the semiconductor substrate to create an aperture, and plating the aperture with a conductive material. Plating the aperture can include either pattern plating with a resist mask or blanket plating without a resist mask. Both plating techniques have certain drawbacks. For example, in addition to the other TSV processes, pattern plating includes forming a resist layer, patterning the resist layer, and removing the resist layer after plating, and/or other additional processing stages. On the other hand, even though blanket plating does not require as many steps as pattern plating, blanket plating creates a large amount of excess conductive material on the surface of semiconductor substrate. The excess conductive material must be removed before subsequent processing stages, which takes time and wastes the conductive material. As a result, there remains a need for improved techniques for forming TSVs in semiconductor substrates.